Metering valve for aerosols

ABSTRACT

A metering valve to be fitted to an aerosol container comprises a dispensing member (6) in the form of a tube and a metering member (2) in the form of a cylindrical cup which receives the inner end of the tube (6). The dispensing tube (6) is slidable in an opening in a valve housing (11). A bellows (1) extends between the inner end of the dispensing tube (6) and the housing (7) to seal against escape between the dispensing tube (6) and the opening in the valve housing (7). The inner end of the dispensing tube (6) bellows (1) seals against a seat (9) in the floor of the metering cup (2). The upper end of the metering cup (2) seals against a seat (3) which lies against the upper end of the bellows (1).

BACKGROUND AND SUMMARY OF THE INVENTION

This invention relates to a metering valve for aerosols.

Valves are known which are affixed to aerosol cans and are designed torelease one measured dose of product/propellant mixture per actuation.These valves are typically used with medicinal aerosols, such as MeteredDose Inhalers for treating asthma and other conditions, where theproduct is a powdered drug suspended in a liquid propellant. There is apresent need for a design of metering valve which does not employ anysliding sealing faces because some products or powders can migrate pastthis type of seal and cause leakage or incorrect dosage. Examples ofaerosols utilising sliding seal type metering valves are shown in U.S.Pat. No. 3,301,444.

U.S. Pat. No. 2,835,417 describes a metered dosage valve for a containerof fluid under pressure. The valve has a tubular measuring chamberhaving a resilient sealing gasket at one end with a central openingthrough which a hollow valve stem extends into the measuring chamber.The stem is depressable to close a normally open discharge passage fromthe measuring chamber and then supply fluid to the measuring chamber.When the valve stem is moved downwardly from its normal position, thecentre portion of the gasket is bent downwardly so that when thedownward force on the stem is released, the resilient gasket acts tourge the valve stem upwardly to its initial position.

Although this seal does not involve a sliding action, after repeateddeformation resulting from operation of the stem the gasket is likely todeteriorate and become less resilient which would lead to lessefficiency in the sealing of the valve and allow migration of productsor powders past it. Furthermore, it could lead to less effective sealingagainst the valve stem which would lead to the same problems mentionedabove in that some products or powders could migrate past the seal andcause leakage or incorrect dosage.

Therefore according to the invention, there is provided a metering valveto be fitted to an aerosol container for dispensing a product, saidvalve comprising a housing, a metering chamber located within saidhousing and a hollow actuator stem extending into the chamber andaxially slidable relative thereto, the metering chamber and actuatorstem being moveable into and out of positive sealing contact withoppositely facing valve seats provided on the valve housing and themetering chamber respectively, and sealing means being provided betweenthe actuator stem and the housing and fixed to the housing such thatrelative movement between the stem and housing is permitted,characterised in that the sealing means consist of a flexible web ormembrane fixed to the actuator stem.

The provision of oppositely facing valve seats with a fixed flexiblemembrane or web averts the use of sliding or deforming seals resultingin a considerably improved metering valve.

In each of the metering valves described in U.S. Pat. No. 3,301,444, afurther problem arises in that the metering chamber which receivesaerosol prior to dispensing is refilled with a fresh dose of aerosolimmediately after the previous dose of aerosol has been dispensedtherefrom. The fresh dose then remains in the metering chamber until thevalve is subsequently operated to dispense the next dose. Such anarrangement is disadvantageous in that the fresh does of aerosol cantend to drain from the metering chamber at least to some extent over aperiod of time. When that happens, the next dispensed dose will beincomplete and can have undesirable consequences for a person suffering,for example, from asthma where the correctness of the initial dose isimportant. Moreover, where a fresh charge of aerosol remains in themetering chamber for a long period of time, the suspended drug cansettle in the chamber and will not be properly discharged from thedispensing chamber when the next dose is dispensed.

The invention further provides that the metering chamber receivesaerosol for dispensing by the actuator stem and the sealing contact ofthe metering chamber against its associated valve seat prevents a freshcharge of aerosol entering the metering chamber after a previous chargehas been dispensed therefrom, until the metering chamber and associatedseal are subsequently separated by operating the valve to dispense afurther dose.

With such a valve, the metering chamber is not refilled with a freshdose of aerosol until the user of the aerosol next operates the valve todispense the aerosol. Therefore, fresh doses will not be left in themetering chamber for periods of time between dispensings.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred form of the invention will be described, by way of example,with reference to the accompanying drawings, in which:

FIG. 1 is a cross section through a valve in accordance with theinvention before being fitted to an aerosol container;

FIG. 2 is a cross-sectional view of the valve of FIG. 1 fitted to anaerosol container and showing a filling nozzle applied to the outer endof the dispensing stem;

FIG. 3 is a view similar to FIG. 2, showing the positions of the valvemembers during filling;

FIG. 4 is a cross-sectional view of the top of the filled container ininverted position prior to dispensing; and

FIGS. 5 to 7 are views similar to FIG. 4, illustrating successive stagesof the dispensing process.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG. 1, a valve housing 7 provided with at least one port20 in the upper part of its wall, contains a metering member 2 defininga metering chamber 2a of a size dependent upon the dose to be dispensed.The member 2 is normally urged by a spring 4 into a closed position inwhich its upper end, provided with one or more sealing rings 2b, makessealing contact with the lower face of a valve seat 3 in the form of agasket to form inlet valve means to isolate the chamber 2a; from theinterior of the housing 7. The chamber 2a contains a further valve seat9, which may be made of a compatible elastic material such as syntheticrubber, for sealing contact with the lower end of a dispensing memberstem 6 when the latter is moved into its closed position to form outletvalve means to isolate from the chamber 2a the interior of the stem,which defines an outlet. The stem 6, which may contain a constriction 19to assist atomization of the aerosol mixture, is centralised andsupported for linear movement relative to the member 2 by a guide 5which may be extended, as shown, to limit return travel of the stem. Theinner end of the stem 6 is secured to or formed integrally with one endof a membrane or web in the form of a resilient bellows 1. The bellowsmay have a helical, thread-like form to facilitate moulding fromplastics. The other end of the bellows 1 bears against a shoulder formedon the guide 5 and is provided with an external flange which is clampedbetween the top of the housing 7 and the valve seat 3 by a ferrule 11which may be made of an aluminium alloy and also serves to secure theguide 5 and a sealing ring 8 for engagement with the mouth of an aerosolcontainer when the ferrule is secured to the container by crimping, asshown in FIG. 2. The bellows 1 prevents leakage of aerosol between thestem 6 and the open end of the housing 7 and in particular between theexternal surface of the stem 6 and the The resilient membrane or webnormally biases the actuator stem away from valve seat 9.

The container may be pre-filled before fitting the valve or filled withthe valve in position using a pressure filling machine in the mannerillustrated in FIGS. 2 and 3.

Referring to FIG. 2, the nozzle of the filling machine is applied to theouter end of the stem 6 which moves downward into sealing engagementwith the valve seat 9. The supply of mixture under pressure through thestem 6 acts on the lower end of the chamber 2 which moves downward intoits open position to permit the mixture to pass from the stem 6 throughthe chamber 2 and into the container through the port 20, as illustratedby the arrows 21 and 22 in FIG. 3.

When the container has been filled the valve members return to thepositions shown in FIG. 1 and FIG. 4, the latter showing the containerinverted prior to dispensing a metered dose of its contents.

For dispensing, an actuator (not shown) is affixed to the outer portionof the stem 6 and the latter is moved upward in the direction of thearrow 12 in FIG. 5 to bring the base of the stem into sealing engagementwith the valve seat 9 to isolate the metering chamber from atmosphere asindicated at 13 in FIG. 5. Further movement of the stem 6 in thedirection of the arrow 14 in FIG. 6, moves the open end of the chamber 2away from the valve seat 3 (which is oppositely facing with respect tothe valve seat 9) to allow the aerosol mixture from the container tofill the chamber 2a as indicated at 15 in FIG. 6 and provide the metereddose therein. The valve is then primed ready for dispensing, and bymoving the stem 6 in the opposite direction, as indicated by the arrow16 in FIG. 7, the contents of the chamber 2 are expelled through thestem, as indicated by the arrows 18 in FIG. 7, and when the actuator isreleased the stem is returned to its original position by the bellows 1and the spring 4. Instead of the stem 6 passing through the centre ofthe bellows 1, the latter may be inverted and the stem affixed to itsupper end.

It will be appreciated that the metering chamber 2a remains empty afterthe metered dose therein has been dispensed by operation of the stem 6.Only upon subsequently operating the stem 6 to dispense a further doseof aerosol will the metering chamber 2a refill to provide anothermetered dose.

The valve housing 7 is also capable of acting as a dip cup when theaerosol container is required to be emptied in an inverted position. Forthat end the port 20 in the wall of the valve housing 7 is provided atthe highest point of the main container cavity. The port 20 is thus atthe lowest point of the cavity when the container is upside-down for useand so the entire content of the container can drain through the port 20for dispensing.

Also a small tube 30 indicated in broken lines in FIG. 2, may bepositioned with one end sealingly located in the port 20 and itsopposite end positioned near the closed lower end of the container. Whenthe user operates the valve with the container in the FIG. 2 position,aerosol will travel up the tube 30 and into the chamber 2a.

Instead of providing a resilient bellows 1, a non-resilient flexiblemembrane or web may be provided to prevent leakage of aerosol betweenthe stem 6 and the open end of the housing 7. Pressure of the aerosol inthe metering chamber 2a will be sufficient to move the stem 6 away fromthe valve seat 9 to dispense the aerosol but, if necessary, the stemcould be biased normally away from the valve seat 9 by means of aspring, eg, as indicated at 32 in broken lines in FIG. 1.

The term "aerosol" as used herein includes a pressurised dispensingcontainer charged with a liquid product and pressurised by a liquidpropellent which is volatile at room temperature. The term "aerosol" asa term of art also refers to the liquid in the container as required bycontext.

I claim:
 1. A metering valve to be fitted to an aerosol container fordispensing a product, said valve comprising:a housing; a meteringchamber located within said housing; a hollow actuator stem extendinginto the chamber and axially slidable relative thereto, the meteringchamber and actuator stem being moveable into and out of positivesealing contact with oppositely facing valve seats provided on the valvehousing and the metering chamber respectively; and sealing means beingprovided between the actuator stem and the housing and fixed to thehousing such that relative movement between the stem and housing ispermitted, wherein the sealing means consist of a flexible web ormembrane fixed to the actuator stem; and the resilient membrane or webis a bellows assembly.
 2. A metering valve according to claim 1, whereinbias means is provided for normally biasing the actuator stem away fromthe valve seat on the metering chamber.
 3. A metering valve according toclaim 1, wherein the membrane or web normally biases the actuator stemaway from the valve seat on the metering chamber.
 4. A metering valveaccording to claim 1, wherein the membrane or web partly defines saidmetering chamber.
 5. A metering valve according to claim 1, wherein thepositive sealing contact with the valve seats provides an outlet valvemeans for sealing an outlet in the actuator stem from the meteringchamber and inlet valve means for sealing the metering chamber from amain reservoir.
 6. A metering valve according to claim 5, wherein theinlet valve means can only be opened when the outlet valve means isclosed.
 7. A metering valve according to claim 5, wherein the inletvalve means is opened by movement of the actuator stem.
 8. A meteringvalve according to claim 7, wherein linear movement of the actuator stemover a first distance closes the outlet valve means and further movementin the same direction over a second distance opens the inlet valve meanslinear movement in the reverse direction operating the valve means inreverse.
 9. A metering valve according to claim 5, wherein the outletvalve means comprises the valve seat mounted on the metering chamber.10. A metering valve according to claim 9, wherein said metering chamberdefines an open end for sealing engagement with the valve seat on saidhousing and is provided at its closed end with the valve seat of theoutlet valve means.
 11. A metering valve according to claim 1, whereinthe metering chamber defines a cylindrical cup which receives the innerend of the actuator stem.
 12. A metering valve according to claim 5,wherein the seat of the inlet valve means is mounted on the housing. 13.A metering valve according to claim 12, wherein bias means is providedcharacterized in that the cylindrical cup also receives at least part ofthe bias means.
 14. A metering valve according to claim 8, wherein theactuator stem is returned over the second distance by a second springmeans.
 15. A metering valve according to claim 1, wherein a housing isprovided for the valve which also acts as a dip cup when an aerosol isrequired to be emptied in an inverted position.
 16. A metering valveaccording to claim 1, in which the metering chamber receives aerosol fordispensing by the actuator stem and the sealing contact of the meteringchamber against its associated valve seat prevents a fresh charge ofaerosol entering the metering chamber after a previous charge has beendispensed therefrom, until the metering chamber and associated seal aresubsequently separated by operating the valve to dispense a furtherdose.